Heretofore, bio-mass burners have been used to burn a variety of fuels. Typical examples of these are found in U.S. Pat. Nos. to Hand et al 4,295,956; 4,341,199 and 4,475,471. The grate structure used in these patents has been especially troublesome because of the stresses and strains encountered when the temperature varies from room temperature to approximately 1800 degrees F. to 2800 degrees F. While it has been known to use low ash content fuels, a problem exists, nevertheless, with respect to ash removal from the burning chamber.